Microstructural Characteristics and Tribological Properties of Graphene-Reinforced Magnesium Matrix Composites Fabricated via Rotary Friction Extrusion

The Rotational Friction Extrusion (RFE) technique was successfully employed to fabricate graphite particle-reinforced AZ31 magnesium matrix composites (Gr/AZ31Mg). The microstructure, hardness, and wear properties of the composites were systematically analyzed. The results indicate that the RFE process enables the production of rod-shaped Gr/AZ31Mg composites with well-defined dimensions and high forming quality. The microstructure of the composites consists of fine equiaxed grains formed through dynamic recrystallization, with uniformly distributed Gr particles within the magnesium matrix, contributing to enhanced overall performance. Hardness measurements reveal that the addition of Gr significantly influences the hardness of the composites, exhibiting an initial increase followed by a slight decline. When the Gr content reaches 1.5 wt.%, the composite's hardness is improved by 20.2% compared to the unreinforced AZ31Mg matrix. Regarding wear performance, Gr particles act as solid lubricants during the friction process, reducing direct contact wear, thereby decreasing wear volume and enhancing wear resistance. The variation trends of the friction coefficient and wear rate align with those of hardness; both parameters initially decrease with increasing Gr content and then exhibit a slight rebound. At a Gr content of 1.5 wt.%, the composite achieves the lowest wear rate of 0.197, representing a 33.7% reduction compared to the RFE-processed AZ31Mg matrix, indicating optimal wear resistance at this reinforcement level.